The present invention relates to on a microcontroller having a self-prompting (self-wake-up) device, particularly for use in electrical adjusting drives.
In a known microcontroller having a self-prompting device, as described in German Patent Application No. 4302 232, which is intended to be used particularly in electrical adjusting drives, it is provided with a control device for specifying an active and an inactive operating state in order to economize on supply power, as well as with an oscillator for emitting a prompting (wake-up) signal. This oscillator is provided outside of the microcontroller and, has a relatively low clock frequency. Besides the prompting of the microcontroller by an internal signal emitted by the watchdog, the prompting is also possible at regular, periodically recurrent time intervals by the external prompting signal supplied by the external oscillator and fed to the control circuit. The prompting takes place independently of the operating state prevailing at the moment. The cycle of this external prompting signal should be calculated in such a way that the microcontroller remains in the inactive state as long as possible, in order to attain low average energy consumption. On the other hand, the cycle should be short enough to be able to react sufficiently quickly to a changed operating situation, it being possible to communicate this via input lines. Therefore, if no internal prompting signal occurs in the meantime, this known microcontroller is always prompted in the rhythm of the external oscillator.
A microcontroller with a self-prompting device having the characterizing features has the advantage of making available a complete assembly, in which a low-frequency oscillator exhibiting low current consumption is integrated into the microcontroller as well, and which, in the event the high-frequency clock-pulse source is not in operation, is advantageously able to supply and operate the microcontroller core with this low clock frequency when there are few functions to be carried out. Consequently, an essential condition is created for it, namely that the microcontroller can be operated in an energy-saving manner, and a buffer capacitor in the control electronics to be provided for emergency cases can be selected to be considerably smaller, and thus can be installed in the control electronics as well.
According to the present invention, this is achieved in that the oscillator is a low-frequency oscillator, that provision is made in the microcontroller for a circuit which, from the low frequency of this oscillator, generates a substantially higher clock frequency for the microcontroller core, that the oscillator is integrated as an original component into the microcontroller as well, and that provision is made for an undervoltage detection circuit, whose output signal is able to be supplied directly to the microcontroller core.
According to one embodiment of the present invention, the circuit for generating the high clock frequency for the microcontroller core is a disconnectible phase-locking loop.
In another embodiment, the microcontroller of the present invention is provided with a prompting circuit which, after a specific time has elapsed, or in response to the occurrence of a specific event, shifts the microcontroller core from the inactive into the active operating state.
In another embodiment, the microcontroller of the present invention is provided with a time-switch logic which, after the expiration of a variably specifiable time span, acts upon the prompting circuit, so that the prompting circuit shifts the microcontroller core from the inactive into the active operating state.
In another embodiment of the present invention, the prompting signal of the prompting circuit activates that circuit which, from the low frequency of the low-frequency oscillator, generates the substantially higher clock frequency for the microcontroller core, in order to shift it from the inactive into the active operating state.
According to another embodiment of the present, the microcontroller of the present invention is provided with a multiplexer, via which the microcontroller core, in certain operating situations, is able to be directly supplied with the frequency of the low-frequency oscillator as its clock frequency.
In advantageous manner, after executing particular functions, the microcontroller core is able to be shifted into the inactive operating state for a specific time span which is adaptable to certain circumstances. In another embodiment of the present invention, the adaptable time span is programmable and is able to be stored in a time-comparison register provided in the time-switch logic.
The microcontroller of the present invention is designed such that the frequency of the low-frequency oscillator is, for example, 100 kHz, and the frequency generated therefrom for the microcontroller core is, for example, 10 MHz
The microcontroller according to the present invention is preferably used for electrical adjusting drives of motor vehicles, and the undervoltage detection is connected directly to the electrical-system voltage, in order to detect undervoltage conditions without time delay.